The formulations of a variety of active pharmaceutical compounds make use of a wide range of polymer coatings such as enteric coatings and other release-modifying coatings to produce a formulation with a desired release profile. These coating materials, which are typically polymer compositions, may be applied as one or more film coatings over a core tablet under controlled conditions to produce a modified-release formulation that may include the tablet covered with one or more layers of different polymer compositions.
Existing tablet coating systems typically include a pan coater used to apply the film coatings to tablet cores to form pharmaceutical compositions. The pan coater may include a coating pan or perforated rotating drum that rotates within the controlled environment inside a cabinet. Within the cabinet, a spraying system may pump a fine mist of coating solution toward tablets within the coating pan under controlled conditions to form a thin film the coating on the tablets. The controlled conditions within the cabinet containing the coating pan result in the solvent portion of the coating solution to rapidly evaporate upon contact with the surface of the tablets, leaving behind the solids portion of the coating solution to form the coating.
The properties of the coated tablets are highly sensitive to variations in the operational parameters of the spraying system as well as the controlled conditions within the cabinet. Typically, the controlled conditions within the cabinet include elevated temperature and low humidity to facilitate the rapid evaporation of the coating solution. To this end, an air handling unit may deliver heated and dehumidified air into the cabinet, where it passes over the tablets within the coating pan and subsequently exhausts out a separate exhaust. This one-way airflow provides a low-humidity heated airflow to dry the tablets, and also transports unused coating solution out of the coating pan via the exhaust flow to provide additional control over the coating process.
To complete the production of coated tablet compositions, the coated tablets may be subjected to an additional curing process to allow the polymer coating to fully cure into a particular form to impart the desired coating properties, such as coating smoothness or pH-dependent solubility. In some cases, the curing process may include exposing the coated tablets to a particular temperature profile for a predetermined time period. In these cases, the additional curing process may be performed within the pan coater. However, for certain polymer materials, the curing process may require process conditions that extend beyond the capabilities of existing pan coaters.
One type of tablet formulation may include ingredients that require an additional curing process conducted at relatively high humidity to impart the desired coating properties. High humidity conditions are at odds with typical tablet coating conditions. In fact, many defects in tablet coating processes, such as picking, sticking, erosion, peeling, and/or frosting are attributed to inadequate drying of the coated tablets, which may in part be attributed to humid coating conditions. Thus, in order to perform a high humidity curing process, coated tablets may be removed to a separate curing chamber for exposure to high humidity as needed. However, transferring the uncured coated tablets to a separate curing chamber may impact tablet quality by exposing the tablets to undesired temperature, humidity and/or mechanical damage during transfer. In addition, the transfer to a separate curing chamber may add additional time and cost to the manufacturing process.
A need exists in the art for a process and method of providing high humidity conditions within an existing pan coater device. Such a process and method may also enhance the quality, production time and production costs of tablet coatings cured at high humidity conditions.